liver physiology

Question 1

how much bile is secreted per day?

Answer 1

250ml-1000ml

Question 2

what are the functions of ITO cells?

Answer 2

secretion of the extracellular matrix of the space of disse. storage of fat and fat soluble vitamins.

Question 3

name some of the channels involved in canaliculi secretion.

Answer 3

MDR1-MDR3 cMOAT

Question 4

describe the journey of bile salts.

Answer 4

produced in the liver, released in bile, reabsorbed by gut in jejunum but mainly terminal ileum and then conjugated in liver to amino acids.

Question 5

what is bile made of?

Answer 5

water, bile salts, cholesterol + lecithin and bilirubin.

Question 6

how are bile salts kept in the gallbladder?

Answer 6

arranged in micelles so that they don’t damage the gallbladder.

Question 7

what increases bile viscosity?

Answer 7

mucin.

Question 8

describe the metabolism of amino acids?

Answer 8

cannot be stored because ineffective energy source. they are deaminated to form a-keto acids. glutamate is deaminated for form a-ketoglutarate and fed into the krebs cycle. NH4+ gets excreted

Question 9

how is a-ketoglutamate formed?

Answer 9

deamination of glutamate.

Question 10

how is pyruvate formed?

Answer 10

deamination of alanine from muscle.

Question 11

describe the glucose alanine cycle.

Answer 11

in muscle, glucose in converted to pyruvate via glycolysis. glycolysis is aminated to form alanine. in this process, glutamate is deaminated to a-ketoglutarate in the presence of the enzyme alanine aminotransferase, and the NH4+ is transferred to pyruvate to form alanine. alanine then travels in the blood to the liver where it is deaminated to form pyruvate again. during this process a-ketoglutarate is aminated to form glutamate, this process also uses alanine aminotransferase. the NH4+ is then put into the urea cycle. the pyruvate formed undergoes gluconeogenesis to form glucose again which gets transported to muscle.

Question 12

how much albumin is produced per day? where does it go?

Answer 12

10g. it travels in the interstitium into lymph and into the thoracic duct to be empties into the left subclavian vein.

Question 13

what is albumins half life? how many binding sites does it have?

Answer 13

16-18 hours. 4, all with difference specific binding sites.

Question 14

which clotting factors are produced by the liver?

Answer 14

all but von willebrand.

Question 15

what are microsomal enzymes? where are they found?

Answer 15

monooxydases. they can oxidise, reduce, or hydrolyse, and glucuronidation. CP450. smooth ER

Question 16

what are nonmicrosomal enzymes? where are they found?

Answer 16

cytoplasm/mitochondria of hepatocytes. protein oxidases, esterases or conjugates.

Question 17

what is phase 1 of detoxification?

Answer 17

phase 1 - cytochrome p450. xenobiotic is oxidised. results in some loss of function of the drug, can still be active. the reaction is non-synthetic. end result is a new/modified functional group.

Question 18

what is phase 2 of detoxification?

Answer 18

conjugation. this reaction is synthetic. it is the attachment of an ionised group to completely inactivate the molecule e.g. methyl or acetyl group. makes it more soluble.

Question 19

what does it mean to say that a reaction is synthetic?

Answer 19

produces a soluble compound that can be excreted in urine/faeces.

Question 20

what is glucuronisation?

Answer 20

most common conjugation reaction in which glucuronic acid is added to the xenobiotic. BILIRUBIN!!!!!

Question 21

what are vitamin A, C, B, D used for/deficiency?

Answer 21

A = retanoids, for seeing in dark. C = for synthesis of neurotransmitters. B = nucleic acid production. D = calcium metabolism.

Question 22

what is BMR equivalent to? how is it measured?

Answer 22

ATP useage. O2 uptake

Question 23

what do the brain, RBCs and liver use for energy?

Answer 23

brain = ketone bodies and glucose. RBCs use glucose. liver uses glucose, fatty acids, alcohol, AAs.

Question 24

what is the total energy expenditure?

Answer 24

60% resting, 30% activity induced and 10% dietary. 70% is from fats and 30% is from carbs.

Question 25

how mud protein do adults turn over per day? secrete? how much reabsorbed?

Answer 25

1-2% of total body weight. 20-30g. 80% reabsorbed, 20% excreted.

Question 26

what are the two types of degradation of proteins?

Answer 26

lysosomal/nonlysosomal.

Question 27

describe lysosomal degradation of proteins.

Answer 27

reticuloendothelial system of the liver. protein diffuses through the fenestrations of the capillaries and kupffer cells engulf and degrade by releasing hydrolytic enzymes.

Question 28

describe nonlysosomal degradation of proteins.

Answer 28

when proteins have reached their half life or have been part of a catalytic reaction, part of the protein called a PEST sequence may be exposed. this exposure causes ubiquitin to bin, a process called ubiquitinisation. this protein is then ‘tagged’ for protein degradation. the protein is taken to a proteasome where it is degraded by proteases. a pest sequence contains proline, glutamic acid, serene and threonine.